A Low-Voltage Low-Power Implantable Telemonitoring System with Application to Endo-Hyperthermia Treatment of In-Stent Restenosis

Abstract

This paper presents a low-voltage low-power implantable telemonitoring system in the context of a smart stent that uses wireless endo-hyperthermia for the treatment of in-stent restenosis. More specifically, an application specific integrated circuit (ASIC) is designed and implemented that senses the ambient temperature and wirelessly transmits the sensory information to a nearby hub. A customized “smart” stent is used as an antenna for wireless data and power transfer over the unlicensed industrial, scientific, and medical (ISM) 915 MHz and 2.4 GHz bands, respectively. For the prototype design, the ASIC is embedded on the small platform at the end of the custom-made stent that also serves as an antenna and the circuit functions without requiring any off-chip components. The proposed fully integrated solution has the following functionalities: radio-frequency (RF) telemetry, power management unit (RF -to-DC converter and voltage regulation), and temperature sensing. The proof-of-concept prototype ASIC is designed and fabricated in a $0.13-\mu \mathrm{m}$ CMOS process and has a chip area of 1.56 mm2. The device can detect and response to the temperature variations in the range of 30 to 50 °C. The remote power link is established when the power received by the implantable device is about −8 dBm. The data can be transmitted from the ASIC to an external hub at the power level of −28.38 dBm, with the total power consumption of 109.6 $\mu\mathrm{W}$.